1. Field of the Invention
The present invention relates to a heat exchanger which is used in a heat exchanger type ventilating device or an air conditioning unit.
2. Discussion of Background
Working or living spaces in, e.g., office buildings, apartments and townhouses are air-conditioned in a wide range, increasing energy consumption for air conditioning. A total heat exchanger which exchanges heat between indoor air and outdoor air can save energy for an air conditioning unit by recovering heat lost in ventilation. A heat exchanger having high heat exchanger effectiveness is required in terms of recovery of heat. It has been widely known that conventional shapes of a heat exchanger are classified into a crossflow total heat exchanger wherein supply air flows perpendicularly to exhaust air, and an opposed flow total heat exchanger wherein supply air and exhaust air flow in opposite directions. An opposed flow total heat exchanger can generally has a higher heat exchanger effectiveness than a crossflow total heat exchanger having the same area of heat transfer surface.
Improvement in performance and miniaturization of total heat exchangers by flowing supply air and exhaust air in opposite directions have been disclosed in, e.g., JP-A-57122289. In FIG. 22, there is shown a perspective view of a schematic structure of the total heat exchanger disclosed in the publication. In this figure, reference numeral 1 designates an opposed flow total heat exchanger, reference numeral 2 designates partitions which have a corrugated central portion, reference numeral 3 designates the corrugated portion of the partitions 2, reference numeral 4 designates uncorrugated flat portions which are formed on opposite ends of the partitions 2, reference numeral 5 designates closed end surfaces which are arranged at the opposite ends of the partitions 2, and reference numeral 6 designates closed side surfaces which are arranged at sides of passages formed by the partitions 2.
Total heat exchange of sensible heat and latent heat is carried out for heat recovery by flowing exhaust air from indoors to a direction indicated by an arrow 7 and flowing supply air from outdoors in a direction indicated by an arrow 8. The supply air and the exhaust air form a passage arrangement in an opposed flow pattern through the partitions 2 to carry out heat exchange effectively. The corrugated portion 3 has a length L4 in a flowing direction longer than a width L5 of the partitions 2.
In FIG. 23, there is shown a cross-sectional view of the total heat exchanger 1 of FIG. 22 taken along the line XXIII--XXIII. The corrugated portion has corrugations and intermediate flat portions alternately formed thereon. When the partitions are put on above one another, the intermediate flat portions are put on the corrugations, and the corrugations are put on the intermediate flat portions to hold required spacing. The respective passages formed by the partitions have an upper portion formed with a corrugation and a lower portion formed with an intermediate flat portion, and have the exhaust air 7 and the supply air 8 flowing in a layered pattern. The spacing G1 between adjacent partitions 2 corresponds to the spacing between adjacent intermediate flat portions at the corrugated portion 3, and the spacing between adjacent flat portions 4 without corrugations is also the same as the spacing between adjacent intermediate flat portions.
Another measure has been disclosed in e.g. JP-A-5924195. In FIG. 24, there is shown a schematic view of the structure of the total heat exchanger disclosed in this publication. In FIG. 24, like or corresponding parts are indicated by the same reference numerals as those parts of FIG. 22, and explanation of such parts will be omitted. Reference numeral 26 designates flat plates, reference numeral 27 designates openings "A", and reference numeral 28 designates openings "B". The flat plates are jointed to corrugated portions 3, and extend longer than the corrugated portions 3 to form the openings "A" 27 with flat portions 4 without corrugations. Units which are formed by jointing the partitions 2 to the flat plates 26 are put one above another to form the total heat exchanger 1. Each of the openings "B" 28 is formed between the flat portion 4 and the flat plate 26 of adjacent jointed units.
The respective openings "A" 27 have spacing G2, and the openings "B" 28 have spacing G3. Heat exchange is carried out by flowing e.g supply air in the openings "A" 27 and exhaust air in the openings "B" 28.
As seen from FIG. 24, the length L7 of the flat plates 26 is longer than the length L6 of the corrugated portions 3 of the partitions 2 because the total heat exchanger 1 separates the supply air and the exhaust air using the partitions 2 and the flat plates 26.
Although the spacing of the openings "A" 27 and that of the openings "B" 28 are not required to be equal, two different fan requirements are needed when pressure loss is different on a supply air side and an exhaust air side. For this reason, the respective flat plates 26 are positioned at a central portion between the flat portion 4 of a partition 2 and the flat portion 4 of its adjacent partition because it is desired to make the spacing G2 and the spacing G3 as equal as possible.
In FIG. 25, there is shown a sectional view of the total heat exchanger 1 of FIG. 24 taken along the line XXV--XXV. The corrugated portions 3 are jointed to the flat plates 26 to form passages. The passages have exhaust air 7 and supply air 8 alternately flowing therein. Although the flat portions 4 of the partitions 2 do not exist in the XXV--XXV section, the flat portions are positioned in a substantially central portion of the corrugated portions 3 as shown by broken lines.
The spacing G2 of the openings "AA" 27 and the spacing G3 of the openings "B" 28 are substantially half of the peak to peak length of a wave which may be considered the amplitude of the corrugated portions 3. Different air flows flow on upper side and a low side of the flat plates 26 to carry out heat exchange through the flat plates 26.
Since the total heat exchanger shown in FIG. 22 has been constructed as stated earlier, two main problems are created. Firstly, it is required that the corrugated portions 3 of the partitions 2 be formed so as to include the corrugations and the intermediate flat portions therebetween alternately, that the corrugations are put on the flat portions at some locations, and that the flat portions are put on the corrugations at the other locations. Otherwise, the spacing G1 of the partitions 2 can not be held. This means that the corrugated portions require high manufacturing accuracy, and that paper or other material which is likely to change its shape depending on temperature or humidity is not suitable for a material of the partitions 2.
Secondly, since the spacing G1 of the partitions 2 is not only the spacing of the corrugated portions 3 but also that of the flat portions 4 without corrugations as shown in FIG. 23, fluid loss becomes great at the flat portions 4, introducing an increase in pressure loss of the heat exchanger. Although the opposed flow exchanger can improve heat transfer property due to opposed flows to make the corrugated portions 3 for heat exchange smaller and the shape more flexible in comparison with the crossflow heat exchanger, the opposed flow heat exchanger have a problem in that pressure loss at the flat portions where air flows are separated is great.
The other conventional heat exchanger shown in FIG. 24 also has the second problems. Because the spacing of the openings "A" 27 and the openings "B" 28 formed between the respective flat portions 4 and the flat plates 26 is substantially half the amplitude of the corrugated portions 3, the pressure loss at portions adjacent the openings to the corrugated portions 3 is greater than the pressure loss at the corrugated portions 3.
As a measure to decrease pressure loss in the entire heat exchanger 1 constructed as stated earlier, it could be considered that the pressure loss in the entirety is decreased by reducing the pressure loss at the flat portions 4 without corrugations because the pressure loss at the flat portions 4 is greater than the pressure loss within the corrugated portions 3. As one of such a measure, it could be considered that the spacing between the flat portions 4 and the flat plates 26 is increased to decrease the flow rate of the air flows so as to reduce the pressure loss. In this case, a decrease in the flow rate at the corrugated portions 3 lowers a heat transfer property because not only the spacing at the flat portions 4 but also the spacing at the corrugated portions 3 for heat exchange becomes large. This means that a larger heat exchange area is required to obtain the same heat exchanger effectiveness, which leads to enlargement of the heat exchanger.
It is an object of the present invention to eliminate these problems, and to provide an opposed flow heat exchanger capable of holding a shape on assemblage in a sufficient manner, minimizing pressure loss and making the size compact.